The significance of cytosolic fumarase for linkage of the urea cycle, malic enzyme and mixed function oxidation (NADPH utilization) to glucose synthesis (especially in diabetes) has been neglected in the biochemical literature. But several recent observations ascribe more importance to this particular enzyme because of the phenomenon of enzyme latency and rapid "activation" by various nutritional and hormonal perturbations such as induction of diabetes. In the present study the role of this enzyme in diabetes and other nutritional and normal conditions with regard to the linkage of urea cycle with carbohydrate metabolism will be investigated.